This invention relates to medical devices, in particular to hemostatic valves for intravascular devices.
Percutaneous placement of intravascular catheters, pacemaker leads, etc. involves blood loss, that while easily controllable, especially during venous access, can become significant during long procedures. For example, procedures such as placement of leads in the coronary sinus for biventricular pacing, can last 4 hours, during which time the blood loss of up to 500-600 cc can represent a risk to the patient. Additionally, the open conduit into the body can become a source of infection to the patient. To help reduce these potential risks, self-sealing hemostatic valves have been developed for use with introducer sheaths. These valves provide a seal against flashback of blood from the proximal end of the sheath, including when a second device is being manipulated within the introducer.
Medical devices with large proximal fittings, such as pacemaker leads and PICC lines, cannot be readily used through standard hemostasis valves and introducers because of the need to remove the introducer while leaving the other device in place. To address this need, splittable sheaths and hemostasis valves were developed so that the introducer and valve can be removed while the inner device remains in the patient. Combinational devices exist, such as the SAFE-SHEATH(trademark) Splittable Valved Sheath System (Pressure Products, Inc., Rancho Palos Verdes, Calif.), which is comprised of a splittable valve attached to the end of a scored introducer sheath. The valve housing containing the valve membrane is split along scores lines which are aligned with score lines that continue down the length of the integral introducer. Thus, the valve and introducer are split together. One disadvantage of this combinational system is the lack of flexibility in how the device is used. For example, to place a coronary sinus pacemaker lead, a physician will often wish to advance the long introducer sheath into the coronary vessel, then partially withdraw the sheath, perhaps 10 cm, prior to introducing the pacing lead. The large integral valve at the proximal end of the sheath cannot enter the patient; therefore, the physician must have an undesirably long section of introducer exiting the patient, where ideally, he or she would like to peel the introducer back closer to the entry site. In addition, the scored introducer portion of the SAFE-SHEATH(trademark) lacks the structural integrity to negotiate tortuous bends of the coronary vessels. Because the valve and introducer are designed only to be used together, the system cannot be adapted to work with different sheaths and other intravascular devices that may offer important clinical advantages in certain procedures.
What is needed is a simple system that offers greater flexibility to fully manipulate and adjust the splittable sheath prior to splitting away the valve. It would also be desirable to have a splittable valve that can be used with different splittable sheaths that did not require integral attachment or alignment of split lines. Further considerations include having a splittable hemostatic valve of simple construction that is easy to use, inexpensive to manufacture, and can provide superior sealing characteristics, even in the presence of high backflow pressures such as are seen in arterial applications.
The foregoing problems are solved and a technical advance is achieved in a splittable hemostatic valve that includes an interfacing region sized and configured to permit the valve to be coupled to a separate splittable introducer sheath or other tubular medical device to permit passage of a catheter or device therethrough with minimal blood flashback. In a first embodiment, the hemostatic valve can be placed over a splittable introducer sheath, such as a PEEL-AWAY(copyright) Introducer Sheath (COOK Incorporated, Bloomington, Ind.) while typically, a dilator is initially co-introduced, followed by the device being placed, such as a pacemaker lead or intravenous catheter having a large proximal hub or fitting. The hemostatic valve can then be split and removed from the introducer, which is also split apart, leaving the indwelling device undisturbed. Advantageously, the replaceable aspect of the valve allows the physician the ability to partially withdraw the introducer and peel it back down, as is often done when placing certain intravascular devices, and then place the hemostatic valve back over the new proximal end that is formed. This provides a significant clinical benefit over existing splittable introducers that include an integral valve at the proximal end that is split along with introducer, thereby not allowing for replacement at a more distal location. In another embodiment, the interfacing region can be configured to be placed at least partially within the passageway of the introducer sheath, instead of over the sheath""s outer surface.
The hemostatic valve comprises a valve body which is typically made of silicone or another elastic material that allows the valve to be fitted over or into the introducer sheath while offering some sealing characteristics. The hemostatic valve includes one or more sealing elements located within the valve passageway. In some embodiments of the invention, one or more of the sealing elements are formed to be integral with the valve body. They can be positioned at the proximal end or within the body of the valve and may include slits or apertures to allow passage of a medical device. Other embodiments include a valve insert disk made of silicone foam that is separately formed and affixed within the hemostatic valve passageway.
In various other aspects of the present invention, the proximal end of the hemostatic valve may be configured to receive and lock a dilator hub such that the dilator and introducer can be maintained in the proper longitudinal alignment with each other during the procedure. In addition, the distal end of the valve can be configured to accept a series of specific-sized introducers by including a multiple steps of different diameters (e.g., 3.5 to 6.0 Fr). In another aspect, the valve can include a side port to allow access to the passageway for procedures such as an I.V. drip, system flushing, air evacuation, or the infusing of medicaments or contrast media.
The hemostatic valve includes at least one line of fissure through which the valve is opened to allow external access to the passageway. In one embodiment, the silicone valve body is formed with opposing scores or grooves formed nearly all the way through the inside or outside of the valve wall such that the two valve halves can be readily pulled apart when the two integral tabs are pulled outward to initiate the split. Typically, the sealing elements are correspondingly scored or split to facilitate a complete separation of the valve assembly.
In another aspect of the invention, the valve is constrained by a splittable outer sheath, such as one made of molecularly oriented, anisotropic PTFE used to make the PEEL-AWAY(copyright) Introducer Sheath. The embodiment also includes a means to grasp and tear the sheath away to open the valve, which may be restrained as two separated halves that fall apart, or scored or so affixed as to be torn apart by the separating action of the sheath.
In another aspect of the invention, the distal portion of the hemostatic valve assembly includes a splittable distal extension of the valve body that is adapted to fit over or couple with a particular medical device. Many intravascular introducers and other devices, unlike the Cook PEEL-AWAY(copyright) Introducer, have a large proximal fitting. In one embodiment, a distal portion is adapted to accept and seal about the proximal fitting of a standard introducer sheath. The distal portion could include a series of seals that are designed to fit over a multiplicity of fittings, making it a xe2x80x98universalxe2x80x99 splittable hemostatic valve.
In yet another aspect of the invention, a sealant filler material is provided within the passageway of the hemostatic valve, preferably within one or more cavities formed between the self-sealing membranes. While the self-sealing membranes provide an adequate barrier against fluid backflow when used in the venous system where pressures typically average around 0.2 psi, arterial pressures represent over a ten fold increase over that of the venous side, making sealing much more difficult. This sealant filler material, which provides an additional blood barrier, can comprise virtually any biocompatible material that can provide a seal around a device being passed through the valve. Possible materials include a viscous liquid such as glycerine; a gel; a foam or sponge; densely-packed solid particles such as minute beads or fibrous material; and strips of material such as collagen. These materials can be affixed to or incorporated into the valve body or introduced into the existing cavity, such as via a side port or injected through the valve body wall. Membranes can be used to longitudinally divide the cavity into two halves that are filled with a substance that allows the subcavities to be resiliently depressed. The resulting counter force against the residing device provides a seal with the membranes allowing the contents of the subcavities to remain contained when the valve is separated.
In still yet another aspect of the invention, a biasing means is included to provide additional force against the leaflets of the distal seal, such as a duck-bill valve, to provide improved sealing properties. In one embodiment, the biasing means comprising two biasing elements of a material such as silicone which are added to the valve after fabrication. The biasing elements are added by applying force to the valve on opposite sides such that the force is in line with a valve slit, thereby causing it to open slightly. The silicone or other material is then added adjacent to the valve leaflets at points perpendicular to the valve slit and allowed to cure. The force is released, returning the valve to its original shape with the cured biasing elements now functioning to continuously urge the leaflets closed. In other embodiments, the biasing means comprises an O-ring or sleeve that is included within the valve after the valve with slit is formed to provide a biasing force to urge the leaflets into the closed position.
In still yet another aspect of the invention, the valve assembly can include a plurality of valves whose passageways are joined distally into a common passageway. In an embodiment having two proximal seals with two passageways each representing bifurcations of the single common passageway, there are two oppositely placed lines of fissure that allow the valve assembly to be separated into two halves. In an embodiment having three proximal seals and three passageways that feed into a single common passageway, there are three lines of fissure that allow the valve assembly to be separated into three pieces to allow introduced devices to remain in place. Additional valves and entry passageways are also contemplated.